Google Keep works in mobile and desktop. It's $free.

I sometimes use Whatsapp (Android) as a fast multimedia todo app. The way it works is that I create a group where I am the only member. I then add an icon on the home screen that immediately takes me to the group so I can start typing, recording voice, taking photos, etc. It doesn't have task statuses or even checkboxes, but it can manage lots of different data formats.